In Vitro Propagation of Everlasting Paper Daisy [Helichrysum bracteatum (Vent.) Andrews] using Shoot Tip Explants

摘要

A reproducible protocol for in vitro regeneration of Helichrysum bracteatum (Asteraceae) by multiple shoot formation from shoot tips was established. Multiple shoot cultures were derived from shoot tip explants of 6-8 days old in vitro seedlings on Murashige and Skoog medium supplemented with 2.5 pM 6-benzylaminopurine. Friable, non-organogenic calli occurring at the base of cultured shoots which interfered with the further growth and rooting of shoots into plantlets was checked by the incorporationof two auxin transport inhibitors, 2,3,5-triiodobenzoic acid (TIBA) and 1-N-naphthylphthalamic acid (NPA) to MS medium containing BAP (2.5 muM). Anatomical studies to trace the origin of multiple shoots revealed the axillary origin of shoot buds in cultures obtained on MS medium with BAP (2.5 muM) and NPA (2.5 muM). NPA promoted the formation and development of shoot buds and prominent vascular connections between the main shoots and new shoot buds. The shoots thus obtained rooted readily on transfer togrowth regulator-free MS medium. Out of the auxin transport inhibitors tested, NPA was more effective than TIBA in forming longer shoots and a greater percentage of root formation. The plantlets acclimatized successfully in the greenhouse indicating thesuccess of the regeneration protocol.